import java.util.ArrayList;

public class tester
{	

	public static void main(String[] args)
	{
		ArrayList <Object> characters = new ArrayList <Object>();
		characters.add(new Astronaut());
		characters.add(new Bullet());
		characters.add(new SpaceShip());
		characters.add(new Klingon());
		
		for (Object character : characters)
		{
			((Movable) character).move(); // Must cast array item to type 'Movable' before calling the 'move' method
		}
	}
}